Pole-Changing and Reversing Cam Switches Selection Guide
When selecting pole-changing and reversing cam switches, compare 1-0-2 reversing/changeover operation, Dahlander two-speed motor wiring, pole count and AC-3 current.
This guide explains what to look for when choosing products in the Pole-Changing Reversing Switches category for three-phase motor reversing (Forward-Off-Reverse), source changeover (1-0-2) and two-speed Dahlander motor control.
Source changeover (1-0-2) vs motor reversing (Forward-0-Reverse)
Rotary changeover cam switches serve two distinct circuit diagrams:
- Source Changeover Switch (1-0-2): Transfers a load between two independent power supplies (e.g. Mains 1 and Generator 2) with a center "0" (Off) isolation position, available in 1P, 2P, 3P and 4P (switched neutral).
- Motor Reversing Switch (1-0-2 / Forward-Off-Reverse): Swaps two of the three supply phases internally to reverse the rotation direction of a three-phase induction motor.
Two-speed (Dahlander / Pole-Changing) motor switches
For two-speed induction motors (such as Dahlander Δ/YY wound motors running at 1500/3000 rpm), 0-1-2 or reversing two-speed (2-1-0-1-2) pole-changing cam switches reconfigure the stator windings between low and high speed.
Pole-changing and reversing switch comparison table
| Selection Criterion | Source Changeover Switch (1 - 0 - 2) | Motor Reversing Switch (Forw - 0 - Rev) | Two-Speed (Dahlander) Pole-Changing Switch |
|---|---|---|---|
| Circuit Function | Switches one load between Source 1 & Source 2 | Swaps two phases to reverse 3-phase motor rotation | Reconfigures motor windings (Δ/YY) for Speed 1 & Speed 2 |
| Pole / Wiring Scheme | 1P, 2P, 3P or 4P (3 Phases + Neutral) | 3P with factory-fitted phase-reversing jumpers | 6-lead Dahlander or separate-winding two-speed diagram |
| Current Rating | 16 A, 25 A, 32 A, 40 A, 63 A, 80 A, 100 A – 315 A | 10 A – 100 A sized to motor AC-3 kW rating | 16 A – 63 A+ sized to high-speed motor full-load current |
| Mounting Options | Panel door, base/DIN-rail or IP65 enclosed box | Panel door, enclosed box or spring-return to "0" | Panel door or machine frame (0-1-2 or 2-1-0-1-2) |
Frequently asked questions
Should I choose a 3-pole or 4-pole 1-0-2 changeover switch for a standby generator?
Always choose a 4-pole (4P) 1-0-2 changeover switch for mains-to-generator transfer so the neutral conductor is isolated and switched alongside the three phases.
Can an operator switch directly from Forward (1) to Reverse (2) while the motor is spinning?
No. Always pause at the center "0" (Off) position until the motor comes to a complete stop before engaging reverse rotation; plugging a spinning motor draws extreme inrush current and arcs the contacts.
When is a spring-return (momentary 1-0-2) reversing switch used?
Spring-return reversing switches automatically snap back to "0" (Off) as soon as the operator releases the handle, making them ideal for hoists, rolling shutters and press tables.